The present invention relates generally to systems and methods for echo cancellation in data communication systems. In particular, the present invention relates to systems and methods for estimation of echo filter coefficients, which are used for echo cancellation.
Echo cancellation finds application in various areas. One such area is the field of multi-carrier data communications. Various multi-carrier communication systems are utilized for transmission of data. One popular multi-carrier technique utilized is Discrete Multi-Tone (DMT). Asymmetric Digital Subscriber Line (ADSL) is a standard that utilizes the DMT technique for high-speed data communication over phone lines. In the ADSL standard, the rate of transmission and reception of data are not equal. Other popular techniques utilized in multi-carrier systems include Orthogonal Frequency Division Multiplexing (OFDM), and frequency division multiplexing (FDM).
Conventional data communication systems utilizing the above-mentioned techniques typically include a Central Office (CO) terminal connected through a physical medium to one or more Customer Premises Equipment (CPE). The physical medium includes copper cable, hybrid fiber, power-line, and wireless medium.
In order to enable communication between the data communication systems, cables and modems are utilized. The modems include necessary circuits, which are adapted to receive and transmit data through the cable. The modem has a transmitter and a receiver that are coupled together through a hybrid circuit. In multi-carrier communication systems that employ Frequency Division Multiplexed (FDM) sub-carriers to transmit data across a communication channel, an echo signal gets introduced in the received signal by the transmitted signal.
The echo signal is introduced in the received signal as a result of the transients introduced in the received signal at frame boundaries. Although transmit and receive bands are separate, some amount of transmit signal leaks into the receive band, thereby generating the echo signal.
The echo signal is introduced into the hybrid circuit through the transmitter and is received along with the received signal at the receiver. In order to enable a decipherable communication, the echo signal needs to be removed from the received signal. The methodology involved in this process includes, reconstruction of the echo signal and echo signal compensation by combining the reconstructed echo signal with the received signal.
Conventional systems and methods available for echo cancellation employ complex training process and are generally not computationally efficient. Further, these systems and methods do not cancel out the echo signal completely. Also, the training process used for estimating the echo filter coefficients is complex.
In light of the foregoing discussion, there is a need for a system and method that employs a simple training process, reduces computational overload, and provides perfect echo cancellation for enabling efficient communication.